Radiotelegraphic station



May 17, 1927. 8

.1. BETHENOD RADIO T-ELEGRAPHIC STATION Filed Aug. 2. 1921' avweutoz JOSEPH BETHENOD W QM/W,

Patented May 17, 1927.

UNITED STATES 1,628,648 PATENT OFFICE.

JOSEPH BETHENOD, OF PARIS, FRANCE.

RADIOTELEGRAPHIC STATION.

Application filed August 2, 1921, Serial No. 489,302, and in Trance February 23, 1918.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, l1 STAT. L, 1313.)

In case metallic towers are used for carrying the radi'otelegra 'ihic antenna, it happens and particularly with high power stations that, due to the effect of mutual induction or 5 capacity between the towers and the different parts of the antenna proper, sometimes high volta e currents are developed in these towers. 11 order to reduce the intensity of these currents (which usually reio duce the carrying capacity to equal the energy supplied to the antenna by the generators), it has been suggested to insulate these towers from the ground. But in practice it is diificult to finda sulticiently good insulation for this purpose and therefore the solution of this problem is still in an imperfectstage. In accordance with the present. invention, these disadvantages are overcome by providing inductances or capacities (or a combination of the two) between the tower and ground. By a suitable proportioning of the values of these inductances and capacities, the intensity of the currents passing between ground and the poorly insulated towers may be materially reduced. in certain cases, even the phase of these currents as related to that of the antenna current may be modified, whereby the radiation of the former will aid that of the latter.

In accordance with a modification of the invention, it will be advisable not to insulate the tower at its base, but on the contrary, the connection between tower and ground should be improved by the best known means.

Similar to the previously described modification, an inductance (or a combination of an inductance and a capacity in series or parallel) is connmted between a suitable point of the tower and the antenna, the value of said inductance being determined depending on the effect to be realized.

More particularly, for a certain value of impedance thus introduced, the current sent to the tower through this inductance will neutralize at the base of the tower the current produced by the capacity of the tower as related to the antenna and to the mutual induction between tower andantenna.

The capacity and mutual induction being really quantities distributed all along the tower, a better result is secured by providing a plurality of inductances between the an tenna and the tower. The values of these inductanccs should generally be unequal and the indnctanccs should be connected at different heights to the tower. in this manner the current produced by capacity and mutual induction may be neutralized at as many points of the tower desired.

Generally speaking, in practice it will be suflicient to neutralize the current at the base only, a complementary arrangement being to double the metallic corners of a copper conductor (preferably a metallic strip, or partial or complete copper plating), and this will present a passage without appreciable resistance to the residual currents in the tower.

Finally as stated at the outset, by means of the mentioned arrangements not only the currents existing in the tower may be substantially neutralized, currents which reduce the useful radiation, but also the direction of these currents may be reversed whereby the radiation of the tower aids the radiation of the antenna. This result will be obtained by adjusting the inductances .in such a man ner that they are traversed by a current superior to the value of the neutralization.

In practice, the,- selt inductances above referred to are mounted on platforms provided for this purpose when the towers are constructed. The self inductances may be on closed within a casing that is filled with oil for the purpose of proper insulation.

If, in. accordance with French Patent e80; 275, a torus is provided near the ground around the tower and this torus is connected in series with a thermic ammeter, the desired value and the best location of these inductances may be easily regulated.

The enclosed drawings are for the purpose of illustration and not limitation and show a schematic arrangement of the above de scribed system. Fig. 1 represents the general arrangement of the mounting of a reactance; Fig. 2 shows a plurality of inductances connected at different heights to the tower; Fig. 3 is a sketch showing the installation of an inductance provided in an oil bath and mounted on a platform of the tower.

In the drawings, 1 is a conductor (crossing conductor) electrically connected with the antenna net work, 2 is an insulator, 3 is the tower, 4 is a reactance, having usually the form of an inductance and a capacity connected in parallel (or only one of these elemerits) and connected on one hand with the antenna 1, and on the other hand with the tower 3. In Fig. 1, 5 is a metallic conductor having the best possible connection with the tower along its entire height and connected with a grounding rod 6 if the base of the tower does not constitute asufliciently good ground connection. Fig. 2 shows the arrangement of a plurality of inductances, each being connected to a particular point of the tower. Fig. 3 represents the physical arrangement of the inductance 4, insulated Within a casing 7. The casing may be filled with oil 8 and has insulated incoming and outgoing terminal posts 9. The whole arrangement is mounted on a platform 10 riveted to the tower.

Having described my invention, what I claim is:

1. In a radio telegraph station, the combination with an energized antenna of a grounded supporting metallic tower insulated therefrom and means to neutralize induction currents in said tower.

2. In a radio telegraph station, the combination of an energized antenna, a grounded metallic supporting tower and a reactanee to neutralize induction currents in said tower connected between said tower and the antenna.

3. In a radio telegra 3h station, the combination of an energize antenna, a grounded metallic supporting tower and a plurality of reaetances connected between said antenna and a plurality of points of said tower.

4. In a radio telegraph station the combination with an antenna of a grounded inetallic supporting tower insulated therefrom and a neutralizing impedance connecting said antenna to said tower, said circuit including a reacta-nce for applying an E. M. F. to the tower equal and opposite to the E. M. F. induced therein by the capacity coupling be tween the tower and the antenna conductor.

5. In aradio telegraph station the combination of an antenna, a grounded supporting tower insulated therefrom, and a plurality of reaetanees of diiterent values, connected between said antenna and points at dillerent heights on said tower, the value of said reactances being such as to neutralize the cur rent produced by capacity and mutual induction at the points to which they are connected.

JOSEPH BETHENOD. 

